Vulcanization of rubber



Patented Dec. 24, 1946 UNITED STATES PATENT OFFICE VULCANIZATION F RUBBER No Drawing. Application May 24, 1944,

Serial No. 537,178

21 Claims.

The present invention relates to vulcanization of rubber and to rubber compositions or such compositions vulcanized in the presence of accelerators, and of accelerators and activators herein described.

In connection with the present invention it has been found that aldehyde condensation products of amidine thiocyanates are highly desirable agents in vulcanization accelerators and particularly as activators for accelerators such as thiazole accelerators including mercapto-arylthiazoles, benzo-thiazyl thiobenzoate, dibenzothiazyl disulfide and others. The above-mentioned condensation products have in themselves accelerating properties, and in addition it is noted that they are particularly valuable for commercial purposes as activators for accelerators in various rubber stocks.

Examples of the condensation products employed in the rubber vulcanization to be described, include diphenyl guanidine thiocyanate formaldehyde condensation product, diphenyl guanidine thiocyanate acetaldehyde condensation product, diphenyl guanidine thiocyanate crotonaldehyde condensation product, diphenyl guanidine thiocyanate butyraldehyde condensation product, such alkaryl guanidine thiocyanate aldehyde condensationproducts as diorthotolyl guanidine thiocyanate formaldehyde condensation product and dixylylguanidine thiocyanate formaldehyde condensation product, and also dinaphthylguanidine thiocyanate formaldehyde condensation product, orthotolylbiguanide thiocyanate formaldehyde condensation product, guanyl urea thiocyanate formaldehyde condensation product, and thelike.

Aldehyde condensation products of the amidine thiocyanates are prepared by gently refluxing under atmospheric pressure or by heating in an enclosed vessel under pressure in case of lowboiling aldehydes, such as acetaldehyde, the thiocyanates with equal or double molar proportions of the respective aldehydes. The ratio of reactants is not critical. Any, excess aldehyde is readily removed'from a given reaction mixture by water washing, distillation or otherwise. To continue the condensation and polymerization- 25 Activator 2 after refluxing, heat is applied to the material in an open vessel. This is particularly desirable if a hard, pulverizable resin product is to be obtained for easier incorporation in a rubber 5 mix.

. Other aldehydic substances that are employed besides those mentioned above in the preparation of the condensation products, are acrolein, benzaldehyde, furfuraldehyde, and polymeric aldehydes.

To illustrate the present invention, the following compositions were prepared:

Composition,

parts by weight Rubber 100 Carbon black Zinc oxide.

Ureka C represents an example of a thiazole, namely, benzothiazolethiol benzoate.

0.1% and 1% of the rubber in a mix are generally satisfactory, a preferred proportion being about 0.4% in the presence of thiazoles.

- The mixes A and B were vulcanized in'a heated mold' for varying times at temperatures indicated in the tables below. Cured rubber products were obtained in each case having the properties tabulated.

Any of the amidine thiocyanate aldehyde con- Table I Normal stress in Time lbs/in. at elonga- Tensile Elongation Activator (with mix A) 323 3 nous of at break, at break,

at 274 F lbs/in. per cent 300% 500% 700% 180 620 2, 300 2, 730 730 d a a a a D'o thot l l n'dine thioc anate crotonaldeh do condensation pro uct 3, 7

Oygua l y y 290 320 3,090 3,420 115 280 710 2, 800 2, 810 693 210 490 1, 890 2, 980 776 260 640 2, 570 3, 590 766 Diorthotolylguanidine thiocyanatc formaldehyde condensation product 320 780 2, 960 3,610 736 310 850 3, 180 3, 690 720 290 780 3, 000 3, 260 713 Table II Normalstress Time in lbs/in. at of cure elongations Tensile Elongation Activator (with mix B) (minutes) oi at break, at break,

. at lbs/in. percent 2,420 565 2, 890 560 .Diortllotolylgllanidine thiocyanate erotonaldehyde condensation product g, (6688 530 5 2,750 436 2,350 550 2, 910 550 Diorthotoiylguanidine thiocyanateformaldehyde condensation product 4 g, (7)33 :3

The following table indicates results obtained It is understood that the invention herein dewith an activator of the type herein used but scribed is not limited solely to the specific emad'ded to rubber mixes at different stages of con- 33 bodiments set forth, and that it is obvious to densation of the thiocyanate and the employed those skilled in the art that many modifications aldehyde, the condensed products designated as such as the application of equivalents and varysolids being more extensively condensed than ing proportions are within the spirit and scope of those designated as viscous: the invention defined in the appended claims.

Table III Time of Moduh at Tens-1e Elongation Activator curs at Strength t b 274 F. 300% 500% 100% per cent 4,155 790 3,930 740 Diphenylguanidine thiocyanatc formaldehyde resin (solid) in mix A 4, 220 770 3,860 750 3,785 750 3,975 795 4,175 770 Diphenylgunnidine thiocyanate formaldehyde resin (viscous) in mix A 4| 245 745 4,225 760 4, 000 760 7 2, 650 01s 3, 635 645 Diphenylguanidinc thiocyanate formaldehyde resin (solid) in mm B 4, 0 5v 0 4,215 615 4,360 565 2, 620' 655 3,500- 675 Diphcnylguamdine thiocyanntc formaldehyde resin (viscous) 1n mix B 3, 930 635 7 4,025 600 4,100- 550 Other accelerator compositions containing What is claimedis: amidine thiocyanate" aldehyde condensation 1. The improvement in vulcanization of rubber Products y be yed that are within t containing accelerators, which, comprises incorscope of we Classes-119119111 defined and may be 65 poration in a rubber mix of a small amount of Substltuted for the speFlfic compoundsexempl? condensation product of the thiocyanate. salt of fied. These condensation products are used in a'g-uanidme withvaldehyda I the vulcamzatmp of any of h rubbery mammals, a 2. Theimprovement invulcanization of rubber that are, vulcamzable including natural rubbers containing accelerators which comprises mum 2331 2 3 ii gi ig ghg f' iia gg ig g f poration in a rubber mix of a small amount of types; or natural or artificially prepared latex condensationproduct of the thiocyanate salt of These are all to be included-herein underthe an a gu amdme Wlth aldehydeterm y v 3; The improvement in vulcanization of rubber The thiocyanates referred to herein arethio- 7 containing a rs, w ich comprises incorcyanate salts. poration in a rubber mix of a small amount of condensation product of the thiocyanate salt of diphenyl guanidine with aldehyde.

The improvement in vulcanization of rubber containing accelerators, which comprises incor poration in a rubber mix of a small amount of condensation product of the thiocyanate salt of diorthotolylguanidine with aldehyde.

5. The improvement in vulcanization of rubber containing accelerators, which comprises incorporation in a rubber mix of a small amount of condensation product of the thiocyanate salt of orthotolylbiguanide with aldehyde.

6. A process of preparing a vulcanized rubber product, which comprises mixing a vulcanizable rubber composition with an accelerator containing condensation product of the thiocyanate salt of a guanidine with aldehyde, and vulcanizing the rubber.

7. A process of preparing a vulcanized rubber product, which comprises mixing a vulcanizable rubber composition with an accelerator containing condensation product of the thiocyanate salt of a diphenylguanidine with aldehyde, and vulcanizing the rubber.

8. A process of preparing a vulcanized rubber product, which comprises mixing a vulcanizable rubber composition with an accelerator containing condensation product of the thiocyanate salt of a diorthotolylguanidine with aldehyde, and vulcanizing the rubber.

9. A process of preparing a vulcanized rubber product, which comprises mixing a vulcanizable rubber composition with an accelerator containing condensation product of the thiocyanate salt of an orthotolylbiguanid with aldehyde, and vulcanizing the rubber.

10. A composition comprising rubber, a vulcanizing agent and an accelerator containing condensation product of the thiocyanate salt of a guanidine With aldehyde.

11. A composition comprising rubber, a vulcanizing agent and an accelerator containing condensation product of the thiocyanate salt of an aryl guanidine with aldehyde.

12. A composition comprising rubber, a vulcanizing agent and an accelerator containing condensation product of the thiocyanate salt of a diphenyl guanidine with aldehyde.

13. A composition comprising rubber, a vulcanizing agent and an accelerator containin condensation product of the thiocyanate salt of a diorthotolylguanidine with aldehyde.

14. A composition comprising rubber, a vulcanizing agent and an accelerator containing condensation product of the thiocyanate salt of an orthotolylbiguanid with aldehyde.

15. A rubber product comprising rubber vulcanized in the presence of condensation product of the thiocyanate salt of a guanidine with aldehyde.

16. A rubber product comprising rubber vulcanized in the presence of a thiazole and condensation product of the thiocyanate salt of a guanidine with aldehyde.

17. A method comprising vulcanizing a rubber in the presence of condensation product of the thiocyanate salt of a guanidine with aldehyde.

18. A method comprising vulcanizing a rubber in the presence of condensation product of the thiocyanate salt of an aryl substituted guanidine with aldehyde.

19. A method comprising vulcanizing a rubber in the presence of condensation product of the thiocyanate salt of a diphenylguanidine with aldehyde.

20. A method comprising vulcanizing a rub her in the presence of condensation product of the thiocyanate salt of a diorthotolylguanidine with aldehyde.

21. A method comprising vulcanizing a rubber in the presence of condensation product of the thiocyanate salt of an orthotolylbiguanide with aldehyde.

WILLIAM H. HILL. 

